Outliner issue - expanding manually
You can restore the default key maps if you go to User Preferences(ctrl+alt+u), Input tab and choose Restore for the Outliner:



You may have conflicting settings in other key maps as well. You could also try searching for everything assigned to mouse buttons.

If all fails, you could restore all key maps to default. If that fails, there might be an add-on that is causing the trouble, you would need to disable all enabled add-ons one by one to find the one causing issues. 

You could rename or delete(maybe backup first) %appdata%\Blender Foundation\Blender\[your version] (on Windows) folder to restore everything to default, but that would disable all installed add-ons as well as your UI color theme.